PSU Requirement for large number of hard drives?

[practal]

Rebuilding my media server and in the market for a new PSU. Previous server build had a high end CPU, gaming GPU, 800w PSU, and a lot of unnecissary things. I never touch the system so I've decided to rebuild a much lower power system. No point in wasting all of that power on a system that is just sharing media.

I currently have the system running minus the hard drives. Its a MODT using a 45nm intel and a Supermicro Storage adapter. I have it ideling well below 20w and full loaded at 31w. I think I can still take the core system lower but haven't messed with it much. I will be adding 8-10 2TB hard drives and this will be adding more wattage later.

I have this system hooked up to the 800w PSU but want to get one much smaller so I can get a better efficiency level. Obviously just about any wattage should work. The big thing Im looking at is the load on the assorted rails. I don't want to buy a 200w PSU that doesn't have enough on the 5v. What kind of 5v rail should I look for? Anything else I should look out for? I'd love to do a Pico but I assume way to much load for 24/7 operation.

[washu]

I don't think you need to worry much about the 5V line. 3.5 HDs run the spindle motor on 12V. If you are worried you can look at the specs of your drives and add up the 5V draw.

I'd say a good 350W would probably be more than enough if you drop the gaming GPU. Onboard or really basic is all you need.

As a point of comparison I have a server with 11 drives, one 2.5 and the rest 3.5. CPU is an E5200, MB is a Gigabyte EP45 series. One extra generic PCIe SATA controller. Video is an old 1 MB PCI card. Running off an Earthwatts 380 with no issues. Measured with a Kill-A-Watt the power on surge is slightly over 200W and it settles down to around 150W just idling with the drives still spinning. Drops to about 70W if the server has been idle long enough and the drives sleep.

Several years ago I ran a server with 12 drives off an old 250W. However the CPU was just a PIII celeron.

[bonestonne]

viewtopic.php?t=40962

best example in a real world setting of "how many drives can a PSU run, and have enough juice for a quad leftover...and then some"

[ilovejedd]

You'd need to worry about the 12V rail as that's the one that's going to see the majority of the load especially during boot. I remember reading specs for the Seagate 7200.11 and it mentioned 2A start-up current.

To give you an idea, this is what my unRAID server pulls as measured by a Kill-A-Watt. I can't remember the exact values but they should be pretty close estimates.

Abit AB9 Pro
Intel Celeron 430
ATI Rage XL 8MB (PCI)
Kingston 2x1GB DDR2 667 SDRAM
Seagate Barracuda 7200.11 1.5TB x9
Sandisk Cruzer Micro 1GB flash drive (to hold unRAID OS)
Corsair 520HX

idle (disks spun down): 70~80W
boot: 280W
parity check: 250W